1. Field of the Invention
The present invention relates to recording apparatuses, and more particularly, to an recording apparatus which performs recording with an ink-jet recording head being moved.
2. Description of the Related Art
As information processing units, such as copiers, word processors, and computers, and communication units, such as facsimile machines, have become widely spread, a recording apparatus for digital image recording using an ink-jet recording head has been rapidly used as an image forming (recording) apparatus for these units. In such a recording apparatus, a recording head assembly (multi-head) is generally used in which a plurality of recording elements is integrated and arranged, and ink is discharged from ink discharging outlets provided for each recording head.
Electric signals are applied sequentially to recording elements of a recording head having the above-described configuration to heat ink, and ink droplets are discharged for recording. Since in the usual case, a carriage on which the recording heads are mounted moves during recording, in one cycle of the recording operation the position on the recording medium of the last recorded dot shifts from that of the first recorded dot. To correct this shift, some apparatuses have a carriage on which a recording head is mounted at an angle with such shift being taken into consideration.
FIGS. 10A and 10B show a recording operation in a case in which a recording head having 48 recording elements arranged in a row is used, the recording elements being divided into 16 blocks each having three recording elements, and 16 heat pulses are applied in a time-division manner to each block for recording. FIG. 10A illustrates recorded-dot positions in a case in which the recording head is mounted to the carriage with no slant angle. The direction in which ink discharging outlets are arranged is in parallel to the direction in which the recording medium is fed. FIG. 10B illustrates recorded-dot positions in a case in which the recording head is mounted at an angle to the carriage. The direction in which ink discharging outlets are arranged is slanted against the direction in which the recording medium is fed.
In a case shown in FIGS. 10A and 10B, recording is performed at a recording density of 360 dots per inch (dpi) in the carriage-move direction. A heat pulse is applied to the recording elements 1, 17, and 33 at the first timing, to the recording elements 2, 18, and 34 at the next timing, to the recording elements 3, 19, and 35 at the further next timing, and so on to the recording elements 16, 32, and 48 at the last timing.
When recording is performed with the recording head being mounted without a slant as shown in FIG. 10A, recorded-dot positions shift as heat pulses are applied to recording elements. When recording is performed with the recording head being mounted at an angle as shown in FIG. 10B, recorded-dot positions do not shift and recording is performed at the ideal positions.
FIG. 11 is a timing chart indicating timing for driving a recording head. As shown in FIG. 11, with a combination of four driving signals (BEi1*, BEi2*, BEi3*, and BEi4*), a heat pulse signal (BkENB) is applied to 16 recording elements sequentially.
Recording data is stored in a data buffer. With the use of a 16-bit bus, recording data is read from the data buffer in units of 16 bits. Recording data is transferred to a 48-bit shift register provided for the recording head by reading 16-bit data three times.
When recording is performed with the recording head being mounted at an angle in the conventional apparatus, it takes much time to read recording data from the data buffer which stores the data.
Since the recording head is mounted at an angle in a case shown in FIG. 10B, a dot group 1101 having 16 dots, a dot group 1102 having 16 dots, and a dot group 1103 having 16 dots, 48 dots in total, are recorded in one recording cycle. When these dots are viewed in terms of forming an image on a recording medium, these dot groups belong to the n-th line, the n-1-th line and the n-2-th line, respectively, if each line of dot positions is counted in the carriage-move direction. In other words, these dot groups are shifted by one line each in the carriage-move direction.
Recording data is usually stored in the data buffer according to the two-dimensional pixel arrangement of an image to be formed. In a case shown in FIG. 10B, for example, recording data corresponding to pixels on the n-th line is stored as a group in the data buffer at an area having successive addresses, recording data corresponding to pixels on the n-1-th line is stored as a group in the data buffer at an area having successive addresses, and recording data corresponding to pixels on the n-2-th line is stored as a group in the data buffer at an area having successive addresses. Therefore, the 16 resulting blocks are driven at different recording timings. When the recording head is mounted at an angle as in a case shown in FIG. 10B, recording data has to be read from the data buffer at different addresses at intervals of 16 bits.
When data read from the data buffer is transferred to the recording head via the 16-bit bus, 16 bits in the n-th line data need to be read for recording at the recording elements 1 to 16, 16 bits in the n-1-th line data need to be read for recording at the recording elements 17 to 32, and 16 bits in the n-2-th line data need to be read for recording at the recording elements 33 to 48, in one cycle of recording. At least three accesses to the data buffer are required.
If recording starts at the recording element 9 (that is, the position shifted by eight recording elements) due to a relationship with feed control for a recording medium, for example, data needs to be read in units of eight bits as in a case shown in FIG. 12B.
In cases shown in FIGS. 10A, 10B, 12A, and 12B, 16 heat pulses applied to a recording head form one group. Since data for each line is stored in the data buffer at an area having successive addresses, in a case shown in FIG. 12A in which recording is performed sequentially from the recording element 1, data is read from the data buffer in units of 16 bits via the 16-bit bus, is transferred to the recording head as is, and the corresponding recording elements are driven. In a case shown in FIG. 12B in which the recording start position shifts by, for example, eight recording elements, however, data has to be accessed in units of eight bits in order to read eight bits in the n-th line from the data buffer for the recording elements 9 to 16, other eight bits in the n-th line from the data buffer for the recording elements 17 to 24, eight bits in the n-1-th line from the data buffer for the recording elements 25 to 32, and eight bits in the n-2-th line from the data buffer for the recording elements 33 to 40.
Therefore the number of times the data buffer is required to be accessed increases to six in one cycle of recording, the occupation rate of the bus in a time unit increases, and system performance decreases.